Process to treat magnetite ore and collector composition

ABSTRACT

The present invention relates to a process to treat magnetite ore containing less than 15 wt % of silica on total ore, the process containing a step of (froth) flotating in the presence of a collector composition that contains 80 to 100 wt % of at least one alkylethermonoamine, less than 20 wt % alkyletherdiamine, all wt % based on total weight of all amine components, and wherein the alkylethermonoamine is an alkylethermonoamine with a degree of branching higher than 1, the alkyl containing 11 to 17 carbon atoms, and further relates to the collector composition that can be used in the process.

The present invention relates to a process to treat magnetite ores with a collector containing alkylethermonoamine.

US 2012/0325725 discloses a flotation reagent for iron ores that contains a composition containing a diamine alkoxylate ester A and an amine B. The amine B may be an etheramine (II) or etherdiamine (III) and many examples of both the etheramines and diamines are mentioned. The use of only or mainly an ethermonoamine is discouraged as it is shown that using a C10ethermonoamine is less effective than using the same compound in combination with a diamine alkoxylate ester compound.

US2014/0021104 discloses a branched C10ethermonoamine for use in a process for enriching an iron mineral from a silicate containing iron ore. The C10ethermonoamine may be used in an admixture with a C13-C15ethermonoamine. This second component has a degree of branching of 0.3 to 0.7. The compounds are used in hematite ores flotation.

US2014/0144290 discloses mixed collector compositions containing an amidoamine and etheramine or etherdiamine. One example of the etheramine is isotridecyloxypropylamine. The mixtures are said to be useful for many separations such as for magnetite. In the Examples it is shown that using only an etheramine gives less favorable results than when mixing with the amidoamine in an undefined type of iron ore, using a branched C10 alkyl-enriched alkylethermonoamine as the etheramine.

WO 2008/077849 discloses amine formulations for reverse froth flotation of silicates from iron ores which are a mixture of an etherdiamine with a second compound that may an ethermonoamine. The ethermonoamine in an explicit embodiment is isotridecoxypropylamine mixed 50/50 with the corresponding diamine. In general the ore is said to be a hematite or magnetite ore, the one used in the Example seems to be undefined.

U.S. Pat. No. 3,363,758 discloses the use of etheramines in froth flotation such as to separate siliceous materials from iron ore such as magnetite. The etheramine can preferably be a C7-13etheramine, and explicit examples include an unbranched n-tridecoxypropylamine.

WO 93/06935 discloses the flotation of iron ores by using a collector containing an etheramine and another anionic or nonionic collector. The etheramine is a C6-C22 ether mono-, di-, tri- or tetraamine. The ores can in general be hematite or magnetite. One collector is a C8-C12etherpropylamine for use in hematite ore treatment. The results suggest that the ethermonoamine is beaten by the etherdiamine for magnetite treatment, as for magnetite only diamines are explicitly disclosed.

US2014/0048455 discloses the use of ether mono- and diamines in flotation for enriching an iron mineral from silica-containing iron ore. The preferred etheramine is a branched C13etherpropylamine. The results presented in the document suggest that the ethermonoamine is beaten by the corresponding etherdiamine in performance in hematite. Though the document seems to suggest that the formulations disclosed therein will also work for other iron ores, especially iron ores with high silica content, no results are presented as evidence of this.

There is a continued need for a higher efficiency, in particular in terms of a better selectivity in separation of desired components and impurities, and hence an improved and higher recovery of magnetic iron oxide ores that have a low silica (SiO₂) content.

Accordingly, the present invention provides a process to treat magnetite ore containing less than 15 wt % of silica on total ore, the process containing a step of (froth) flotating the ore in the presence of a collector composition that contains 80 to 100 wt % of at least one alkylethermonoamine, less than 20 wt % alkyletherdiamine, all wt % based on total weight of all amine components, and wherein the alkylethermonoamine is an alkylethermonoamine with a degree of branching higher than 1, wherein the alkyl contains 11 to 17 carbon atoms.

We have now established that, contrary to the above state of the art disclosures, monoamines are much more efficient than diamines in treating magnetite ores in a (reverse) flotation process. It has been established that the use of a collector composition containing as amines predominantly alkylethermonoamines provides for unexpected good results in a flotation process to remove silica from magnetite ore, said results being 30% better than for corresponding alkyletherdiamines. Besides, diamines are less desirable from a health, safety and environmental perspective as they are associated with higher toxicity compared to monoamines.

Magnetite ores are magnetic iron oxide ores that contain magnetite, i.e. Fe3O4. Such ores are typically called magnetite ores, but also other ores can contain magnetite, which in some cases are referred to as magnetic ores, like magnetic taconite ores. Magnetite ores can be distinguished from hematite ores which contain hematite, i.e. Fe2O3.

By “the degree of branching” (DB) as used herein is meant the total number of (terminal) alkyl—such as methyl—groups present on the alkyl chain minus one. It should be noted that degree of branching is an average value for the alkylethermonoamine and hence does not have to be an integer.

In the process of the invention the at least one alkylethermonoamine contains 11 to 17 carbon atoms. In many embodiments the alkylethermonoamine is not a single pure compound but a mixture of alkylethermonoamines in which several alkyls are present. In all these embodiments it is appropriate to define an average alkyl carbon number, giving the average number of carbons of the alkyl chain in the alkylethermonoamine components. This average alkyl carbon number is preferably 11 to 15, even more preferably 11 to 14, most preferably 12 to 14. It was found that C10alkyl-enriched monoethermonoamines, i.e. alkylmonoetheramines that have an average alkyl carbon number lower than 11, usually of around 10, are less desirable for magnetite treatment as they can create too much froth to be efficient.

In a preferred embodiment the alkylethermonoamine contains between 50 and 100% isotridecyl(C13)etherpropylamine, 0 and 50% of isododecyl(C12)etherpropylamine, 0 and 30% of isoundecyl(C11)-etherpropylamine, 0 and 30% of isodecyl(C10)etherpropylamine, 0 and 30% tetradecyl(C14)etherpropylamine, all % being based on total weight of alkylethermonoamine. In a more preferred embodiment the alkylethermonoamine contains between 60 and 93% isotridecyl(C13)-etherpropylamine, 5 and 30% of isododecyl(C12)etherpropylamine, 0 and 10% of isoundecyl(C11)etherpropylamine, 0 and 10% of isodecyl(C10)-etherpropylamine, 2 and 10% tetradecyl(C14)etherpropylamine, all % being based on total weight of alkylethermonoamine.

In another preferred embodiment the alkylethermonoamine contains between 0 and 30% isotridecyl(C13)etherpropylamine, 0 and 30% of isododecyl(C12)etherpropylamine, 50 and 100% of isoundecyl(C11)-etherpropylamine, 0 and 30% of isodecyl(C10)etherpropylamine, 0 and 30% tetradecyl(C14)etherpropylamine. In another more preferred embodiment the alkylethermonoamine contains between 2 and 25% isotridecyl(C13)-etherpropylamine, 2 and 25% of isododecyl(C12)etherpropylamine, 60 and 95% of isoundecyl(C11)etherpropylamine, 0 and 10% of isodecyl(C10)-etherpropylamine, 0 and 10% tetradecyl(C14)etherpropylamine, all % being based on total weight of alkylethermonoamine.

In a more preferred embodiment the degree of branching of the alkylethermonoamine is between 1.5 and 3.5, most preferred it is from 2.0 to 3.0.

In another preferred embodiment the collector composition contains less than 10 wt %, even more preferably less than 5 wt % of alkyletherdiamine on total amine components.

The process of the invention in an embodiment is a process to treat magnetite ore to enrich iron from silica.

The alkyletherpropylamine compound may be made by reaction of an alkyl alcohol (fatty alcohol) with acrylonitrile, whereafter the obtained intermediate containing a nitrile group is hydrogenated to make primary amine, and the obtained product optionally is partially neutralized.

The collector composition used in the process in an embodiment may contain further components that are known to the skilled person to be of benefit in a process to treat iron ores, such as but not limited to (iron) depressants, frothers/froth modifiers/froth regulators/defoamers, secondary collectors, neutralizing agents, pH regulators, cationic surfactants.

It has been found that the efficiency of the flotation process can be improved when the amine is at least partially neutralized by an acid. The amine may be fully or partially neutralized. Preferably, the amine may be neutralized with a 30 to 70% on molar basis amount of acid, preferably between 40 and 60 molar %. The neutralizing agent can be an inorganic acid, such as hydrochloric acid, or preferably a carboxylic acid, more preferably a C1-C5 carboxylic acid, such as formic acid, acetic acid and propionic acid. In one most preferred embodiment, the amine is neutralized with acetic acid.

In an especially preferred embodiment the collector composition may contain

The collector composition may in an embodiment of the process additionally contain a secondary collector to improve performance. The secondary collector is preferably selected from the group of nonionics, like unbranched and branched fatty alcohols, alkoxylated fatty alcohols, fatty amines, alkylamidoamines, preferably fatty alcohols, or alkoxylated fatty alcohols. Examples of secondary collectors in a more preferred embodiment are branched C11-C17 fatty alcohols, such as iso C13 fatty alcohols, and their ethoxylates and propoxylates.

The weight ratio between the primary collector and the secondary collector is preferably from 15:85, more preferably 20:80, most preferably 25:75 to 99:1, preferably 98:2, most preferably 97:3. All weight ratios herein refer to the ratio of active materials, unless stated otherwise.

The flotation process of the invention is preferably a reversed flotation process. Reversed flotation means that the desired ore is not concentrated in the froth, but in the residue of the flotation process. The process of the invention is preferably a reversed flotation process for low silica magnetite ores, more preferably for ores that contain more than 80 wt % of Fe3O4 on total iron oxide content, even more preferably more than 90 wt %, most preferably 95 to 100 wt %. In another preferred embodiment the ores contain less than 12 wt %, even more preferably less than 10 wt %, of silica on total solids weight in the ore. In a reversed flotation process for concentrating magnetite iron ores, the pH during flotation in a preferred embodiment is suitably in the range of 5-10, preferably in the range of 7 to 9.

The reversed froth flotation process of the invention in an embodiment comprises the steps of

-   -   mixing a ground magnetite ore with an aqueous medium, preferably         water;     -   optionally, concentrating the medium with magnetic separation;     -   optionally, conditioning the mixture with a depressant;     -   optionally, adjusting the pH;     -   conditioning the mixture with collector composition as defined         herein;     -   introducing air into the conditioned water-ore mixture;     -   skimming off the froth formed.

The collector composition is very beneficially used in a reversed froth flotation process as claimed, especially in a reversed froth flotation process of magnetite ores to enrich iron.

The composition is preferably liquid at ambient temperature, i.e., at least in the range of 15 to 25° C.

The process of the invention may involve other additives and auxiliary materials typically present in a froth flotation process that can be added at the same time or preferably separately during the process. Further additives that may be present in the flotation process are (iron) depressants, frothers/froth regulators/froth modifiers/defoamers, cationic surfactants (such as alkylamines, quaternized amines, alkoxylates), and pH-regulators.

Depressants include polysaccharides, e.g. dextrin, starch, such as maize starch activated by treatment with alkali, or synthetic polymers such as polyarylamides. Other examples of (hydrophilic) polysaccharides are cellulose esters, such as carboxymethylcellulose and sulphomethylcellulose; cellulose ethers, such as methyl cellulose, hydroxyethylcellulose and ethyl hydroxyethylcellulose; hydrophilic gums, such as gum arabic, gum karaya, gum tragacanth and gum ghatti, alginates; and starch derivatives, such as carboxymethyl starch and phosphate starch. The depressant is normally added in an amount of about 10 to about 1,000 g per ton of ore. After conditioning of the ore, the ether monoamine can be added, preferably partially neutralized, and the mixture is further conditioned for a while before the froth flotation is carried out. If desired, froth regulators can be added before the froth flotation. Examples of suitable froth regulators are methylisobutyl carbinol and alcohols having 6-12 carbon atoms which optionally are alkoxylated with ethylene oxide and/or propylene oxide, especially branched and unbranched octanols and hexanols. After completion of the flotation, a silica-enriched flotate and a bottom fraction rich in iron and poor in silica can be withdrawn.

In another aspect, the present invention relates to a pulp comprising crushed and ground magnetite ore, a collector composition as defined herein, and optionally further flotation aids. These flotation aids may be the same as the above other additives and auxiliary materials which can be typically present in a froth flotation process.

The amount of the collector used in the process of reversed flotation of the present invention will depend on the amount of impurities present in the ore and on the desired separation effect, but in some embodiments will be in the range of from 1-500 g/ton dry ore, preferably in the range of from 10-200 g/ton dry ore, more preferably 20-120 g/ton dry ore.

EXAMPLES Example 1

Materials and Method

Ore in Flotation Tests:

Magnetite ore: Fe₃O₄—87% (Fe—63.0%), SiO₂—9.7%, −44 μm—96%

Flotation Chemicals

Collector composition 1 (comparative) containing about 10 wt % acetic acid and about 90 wt % alkyletherpropylaminepropylamine (i.e. a diamine) wherein the alkyl has a degree of branching of about 3.0 and about 70% of the alkyl group is C13, about 20% C12 and the remainder C11 or lower or C14 or higher alkyl. Collector composition 2 containing about 10 wt % acetic acid and about 90 wt % alkyletherpropylmonoamine wherein the alkyl has a degree of branching of about 3.0 and about 70% of the alkyl group is C13, about 20% C12 and the remainder C11 or lower or C14 or higher alkyl.

Synthetic Process Water

Synthetic process water was used in the flotation tests. It was prepared by adding appropriate amounts of commercial salts to deionized water, following the composition described by chemical analysis of process water from plant, Table 1.

TABLE 1 Composition of flotation process water used in in the lab tests pH Ca, mg/l Mg, mg/l SO₄, mg/l Cl, mg/l HCO₃, mg/l Approx.. 8 70 65 900 1000 85

Flotation Procedure

The study was done as a stepwise rougher flotation with a Denver laboratory flotation machine. The machine was modified and equipped with an automatic froth scraping device and a double lip cell. For apparatus parameters see Table 2.

The ore sample was added to the flotation cell and the cell filled with synthetic process water (37% solids). Water temperature of 19-22° C. was used as standard. The rotor speed was constant during the test, 900 rpm.

-   -   1. The pulp was conditioned for 2 minutes.     -   2. The collector solution (1 w %%) was added and conditioned for         2 minutes.     -   3. Air and automatic froth skimmer were switched on at the same         time     -   4. The flotation continued for 3 minutes. Water was added         continuously by a tube below the pulp surface to keep the right         pulp level.     -   5. The flotation was repeated twice from (2).

The material from the different flotation steps was then dried, weighed out and analyzed for iron and silica content with XRF method.

TABLE 2 Flotation machine parameters Denver flotation machine Cell volume (1) 1.3 Solids in pulp (%) 37 Rotor speed (rpm) 900 Airflow (l/min) 2.5 Scrape frequency (min⁻¹) 15

Preparation of Chemicals

The collectors were dispersed in water and added as a 1%-solution.

Frothing Procedure

-   -   conditioning of the collector and mineral slurry in the process         water for 2 minutes at 900 rpm     -   aeration at a constant rate of 2.5 L/min;     -   the froth formation was followed for 10 minutes or until the         maximum height was reached and stabilized;     -   the froth formation and froth breakage was followed by measuring         the height of the froth every 20 seconds during each process.

Results

The results of the flotation process are given in Table 3 below.

TABLE 3 Fe-concentrate Total Dosage (g/t) Fe-Recovery (%) Grade SiO2 (%) Reagent step 1 step 2 step 3 step 1 step 2 step 3 step 1 step 2 step 3 Collector 60 90 120 80.74 67.39 56.59 4.84 3.19 2.40 composition 2 Comparative 60 90 120 95.10 85.60 70.93 7.36 5.35 3.50 composition 1

Flotation

As one can see from Table 3 and FIG. 1, collector compositions 1 and 2 have the same selectivity: at the same grade both surfactants provide the same recovery.

However, the efficiency of these two surfactants is different: in order to obtain 74% Fe recovery around 110-115 g/t of comparative collector composition 1 is needed and 75-80 g/t of collector composition 2 (FIG. 1).

Frothing

In order to show the frothing properties of the collector compositions two frothing experiments were conducted with ore. Dosages of the surfactants needed to obtain 74% Fe recovery were used (FIG. 1).

As one can see from the results, collector composition 2 in accordance with the present invention creates more froth than comparative collector composition 1, but the created froth is breaking fast (see FIG. 2).

Conclusions

It was found that the efficiency of collector composition 2 is at least 30% higher at the same grade/recovery target than the one provided by comparative collector composition 1. Alkylethermonoamine gives an improved performance in treating low silica magnetitite ores when compared to alkyletherdiamine.

Example 2

Materials and Method

Example 2 was performed using the ore and the process as described for Example 1 above unless indicated differently below.

Collector composition 2 containing about 10 wt % acetic acid and about 90 wt % alkyletherpropylmonoamine wherein the alkyl has a degree of branching of about 3.0 and about 70% of the alkyl group is C13, about 20% C12 and the remainder C11 or lower or C14 or higher alkyl was now compared with a Comparative Collector composition 3 in which more than 99% of the alklyletherpropylmonoamine is based on isotridecanol C13 alkyl with a DB of 2.2.

Results

The results of the flotation process are given in Table 4 below.

TABLE 4 Fe-concentrate Total Dosage (g/t) Fe-Recovery (%) Grade SiO2 (%) Reagent step 1 step 2 step 3 step 1 step 2 step 3 step 1 step 2 step 3 Collector 60 90 120 80.74 67.39 56.59 4.84 3.19 2.40 Composition 2 Comparative 60 90 120 86.95 73.72 62.35 5.71 3.92 2.90 Composition 3

CONCLUSIONS

The key to a successful flotation collector is to have high recovery of the value mineral and high reduction of gangue minerals at the lowest possible dosage of flotation chemicals including the collector. Comparing the results in a grade-recovery plot it is obvious that collector composition 2 of the invention is more efficient than comparative collector compositions 1 and 3 without losing any selectivity. 

1. Process to treat magnetite ore containing less than 15 wt % of silica on total ore solids, the process containing a step of (froth) flotating in the presence of a collector composition that contains 80 to 100 wt % of at least one alkylethermonoamine, less than 20 wt % alkyletherdiamine, all wt % based on total weight of all amine components, and wherein the alkylethermonoamine is an alkylethermonoamine with a degree of branching higher than 1, the alkyl containing 11 to 17 carbon atoms.
 2. Process of claim 1, wherein the alkylethermonoamine contains between and 100 wt % isotridecyl(C13)etherpropylamine, 0 and 50 wt % of isododecyl(C12)etherpropylamine, 0 and 30 wt % of isoundecyl(C11)etherpropylamine, 0 and 30 wt % of isodecyl(C10)-etherpropylamine, 0 and 30 wt % tetradecyl(C14)etherpropylamine, all wt % being based on total weight of alkylethermonoamine.
 3. Process of claim 1 wherein the alkylethermonoamine contains between and 30 wt % isotridecyl(C13)etherpropylamine, 0 and 30 wt % of isododecyl(C12)etherpropylamine, 50 and 100 wt % of isoundecyl(C11)etherpropylamine, 0 and 30 wt % of isodecyl(C10)-etherpropylamine, 0 and 30% tetradecyl(C14)etherpropylamine, all wt % being based on total weight of alkylethermonoamine.
 4. Process of claim 1 wherein the degree of branching of the alkylethermonoamine is between 1.5 and 3.5.
 5. Process of claim 1 wherein the collector composition contains less than 5 wt % of alkyletherdiamine on total amine components.
 6. Process of claim 1 wherein the process to treat magnetite ore is a process to enrich iron from silica.
 7. Process of claim 1 wherein the process is a reverse flotation process.
 8. Process of claim 1 wherein the collector composition contains further additives selected from the group of depressants, froth modifiers, pH regulators, and neutralizing agents.
 9. Process of claim 1 wherein the collector composition additionally contains a secondary collector, preferably selected from the group of branched alkyl fatty alcohols and alkoxylated alkyl fatty alcohols.
 10. Process of claim 1 wherein the ore contains less than 10 wt % of silica on total ore solids.
 11. Collector composition containing 80 to 100 wt % of at least one alkylethermonoamine, less than 20 wt % alkyletherdiamine, all wt % based on total weight of all amine components, and wherein the alkylethermonoamine is an alkylethermonoamine with a degree of branching higher than 1 and contains between 0 and 30 wt % isotridecyl(C13)etherpropylamine, 0 and 30 wt % of isododecyl(C12)etherpropylamine, 50 and 100 wt % of isoundecyl(C11)-etherpropylamine, 0 and 30 wt % of isodecyl(C10)etherpropylamine, 0 and 30 wt % tetradecyl(C14)etherpropylamine, all wt % being based on total weight of alkylethermonoamine.
 12. Collector composition of claim 11 wherein the degree of branching of the alkylethermonoamine is between 1.5 and 3.5.
 13. Collector composition of claim 11 wherein the collector composition contains less than 5 wt % of alkyletherdiamine on total amine components. 